Advances in micro- and nano-encapsulated phase change materials for solar water applications: A comprehensive review of technological progress and future research directions

This review provides a concise evaluation of advancements in micro- and nano-encapsulated phase change materials (M/N-ePCMs) for improving the thermal efficiency and stability of solar water systems. It examines encapsulation techniques—physical, chemical, hybrid, and industrially scalable—that enhance thermal conductivity, latent heat storage, and environmental durability, addressing challenges like PCM leakage and poor heat transfer. The application of ePCMs in solar water heaters, stills, ponds, and tanks is explored, emphasizing their role in stabilizing temperatures, extending operational periods, and boosting energy efficiency. Insights from experimental and numerical studies highlight performance improvements across various system designs and encapsulation methods. The review also covers relevant modeling frameworks, including solar thermal efficiency, exergy analysis, and storage metrics, summarizing key experimental data to inform future optimizations. Challenges such as cyclic stability, material compatibility in aqueous settings, and cost-effective scalability are discussed, with recommendations for advanced material selection, scalable encapsulation, and hybrid system integration. This work serves as a key resource for developing sustainable, high-performance solar thermal systems in water-scarce and off-grid regions.